Good hypothesis, but not quite right. The line you were looking at is for my old card, an NVIDIA RIVA TNT. Below that Device section is the one for the new card,
at PCI 2:05:0. I also test with a minimal config file created by XFree86 -configure,
with only the new card in the computer. I have attached that file. It fails in the same fashion.

Hello - If there are any Nvidia types listening, I need to get this resolved so that I can get two screens on the computer. It's a work, not play, project, and if I can't get it working within a day or two - Tuesday evening my time, I'll have to return the product and get a Matrox.